An investigation was launched last night amid fears a Russian submarine snagged a fishing boat’s gear and dragged the vessel across the sea.

Skipper Angus Macleod said he and his four crew were “extremely lucky” in the incident after his net was repeatedly pulled in front of his 62ft trawler.

The 46-year-old father-of-two has now lodged incident reports with both the Maritime and Coastguard Agency and the Marine Accident Investigation Branch.

Last night, the Royal Navy said neither it nor any other Nato nations had vessels operating in the area at the time.

And one defence analyst said that a Russian submarine could be the culprit.

Tim Ripley said that Russian vessels may be getting into position to observe Nato’s huge Joint Warrior exercise, which is due to start in the next few weeks.

No one from the Russian Embassy in London was available for comment last night.

The Aquarius was fishing for haddock, monkfish and skate in 360ft of water about 10 miles east of the Butt of Lewis.

Skipper Angus Macleod said he and his four crew had never previously experienced anything like the incident

The crews had two nets out when their boat suddenly slowed down.

The port net moved in front of the boat, while the other continued to lie behind it.

Mr Macleod said he was baffled by what was happening and had to “up the revs” on the engine to try to keep ahead of the net in case it fouled the propeller.

During 15 anxious minutes, the boat was constantly manoeuvred to get in front of the moving net – only for it to go forward again.

“It kept going forward and we had to repeat the manoeuvre four times to stay ahead,” said Mr Macleod.

“The winch became increasingly under strain as we tried to haul the rope.

“There was no way the net was snagged on the bottom. It only ended when the dog rope, which attaches the top and bottom ends of the net, was cut by the propeller.

“I have been at sea for 30 years – and between the five of us there is 110 years experience – and we have never experienced anything like that.

Mr Macleod, of Barra in the Western Isles, added: “The sea conditions were good. We were mystified, we just couldn’t explain it.

The Aquarius developed steering problems as it headed for Stornoway and the port’s lifeboat was launched to tow it to harbour for repairs.

It discovered that four of the five one-inch bolts connecting the steering motor with the rudder had come out and the other was loose.

Mr Macleod said: “I think that something got hold of the dog rope and the trawl wire. The only explanation I can think of its a submarine.

“It missed the nets, which is just as well. All five of us are extremely lucky. I don’t even want to think of the consequences of what could have happened.

The incident cost Mr Macleod an estimated £10,00 in damage and loss of earnings.

Skipper Angus Macleod said he and his four crew were “extremely lucky”

He said: “I have been told that there were no MoD submarines north of Neist Point on Skye – and no Nato submarines in the area.

“But that doesn’t tally with what I was previously told by the coastguard that there was submarine activity in the area when we were fishing. It is possible a non-Nato submarine could be involved.

“It was not a whale – we have had whales in the nets before and the net is all twisted afterwards.”

In January it was reported that the Ministry of Defence was forced to request US military assistance to track a suspected Russian submarine off the coast of Scotland.

A spokesman for Stornoway Coastguard said: “We are aware of the incident and can confirm that reports have been submitted. We are taking the matter seriously.”

No Royal Navy vessels were in the area

Last night the Royal Navy said it had no vessels in the area at the time.

A spokesman for the Royal Navy said: “Usually we don’t talk about submarine movements for security reasons. But I am quite happy to confirm that we have checked and there were no Royal Navy vessels operating in that area at the time.

“Similarly, we have checked with Nato and they also had no vessels operating in that area at the time.”

Defence expert Tim Ripley said: “Earlier in the week we had a report of the Russian armed forces in the Arctic in the north of Russia going on high alert and practising short notice snap surprise exercises.

“Dozens of planes, ships and submarines are on manoeuvres, any Russian submarine would come from the North Cape area.

“With heightened major activity by the Russians it is not a surprise in such a situation to have reports of Russian submarines in the west of Scotland.

“If allied countries are operating in our waters they notify the Royal Navy. The Russians don’t, so it is not a surprise if the Royal Navy know nothing about it.

“It is very surprising for a submarine to snag the nets of a fishing boat, they try to avoid fishing boats because they can damage submarines.

“It is a strong possibility that it could have been a Russian submarine. There are not many big whales any more in the North Atlantic.

“Nato and the Royal Navy are about to stage a huge exercise – operation Joint Warrior – around Cape Wrath and the north of Scotland in April.

“Russia might be putting their submarines into position to watch their manoeuvres.”